Fix ScrollContentPresenter measure/arrange.

Perspex.Controls/Presenters/ScrollContentPresenter.cs

@@ -95,7 +95,10 @@ namespace Perspex.Controls.Presenters
 
             if (child != null)
             {
-                child.Arrange(new Rect((Point)(-this.Offset), finalSize));
+                var size = new Size(
+                    Math.Max(finalSize.Width, child.DesiredSize.Width),
+                    Math.Max(finalSize.Height, child.DesiredSize.Height));
+                child.Arrange(new Rect((Point)(-this.Offset), size));
                 return finalSize;
             }
 

Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj

@@ -92,7 +92,7 @@
     <Compile Include="BorderTests.cs" />
     <Compile Include="DropDownTests.cs" />
     <Compile Include="Presenters\ItemsPresenterTests.cs" />
-    <Compile Include="ScrollContentPresenterTests.cs" />
+    <Compile Include="Presenters\ScrollContentPresenterTests.cs" />
     <Compile Include="ScrollViewerTests.cs" />
     <Compile Include="Primitives\SelectingItemsControlTests.cs" />
     <Compile Include="ListBoxTests.cs" />

Tests/Perspex.Controls.UnitTests/ScrollContentPresenterTests.cs → Tests/Perspex.Controls.UnitTests/Presenters/ScrollContentPresenterTests.cs

@@ -4,7 +4,7 @@
 // </copyright>
 // -----------------------------------------------------------------------
 
-namespace Perspex.Controls.UnitTests
+namespace Perspex.Controls.UnitTests.Presenters
 {
     using System;
     using System.Collections.Generic;
@@ -113,14 +113,10 @@ namespace Perspex.Controls.UnitTests
         [Fact]
         public void Content_Can_Be_Larger_Than_Viewport()
         {
-            Border content;
+            TestControl content;
             var target = new ScrollContentPresenter
             {
-                Content = (content = new Border
-                {
-                    Width = 150,
-                    Height = 150,
-                }),
+                Content = (content = new TestControl()),
             };
 
             target.Measure(new Size(100, 100));
@@ -184,5 +180,13 @@ namespace Perspex.Controls.UnitTests
             Assert.True(target.IsMeasureValid);
             Assert.False(target.IsArrangeValid);
         }
+
+        private class TestControl : Control
+        {
+            protected override Size MeasureOverride(Size availableSize)
+            {
+                return new Size(150, 150);
+            }
+        }
     }
 }